1. Field of the Invention
The present invention relates to a semiconductor device that includes a plurality of capacitors having different capacities. More specifically, the invention relates to a semiconductor device that includes an improved RF (radio frequency) capacitor having an MIM (metal-insulator-metal) structure.
2. Description of the Related Art
RF MIM capacitors are elements essential for embedding an analog circuit and a digital CMOS circuit on a single chip. Recently, it has been proposed to use a high dielectric film, such as a Ta2O5 film, as a capacitor insulation film in order to reduce the area of the occupation of MIM capacitors (Jpn. Pat. Appln. KOKAI Publication No. 2001-177057).
The high dielectric MIM capacitor using a Ta2O5 film or the like has the same capacity as that of a conventional one though its area is small, whereas it has a drawback of increasing a leakage current. This drawback is caused for the following reason. Because of oxidation of the surface of a lower electrode and reaction with the material thereof at the time of formation of a Ta2O5 film, oxygen deficiencies due to a plasma atmosphere at the time of formation of an upper electrode, and the like, a leakage current flowing through the Ta2O5 film becomes difficult to control.
Some capacitors used for a semiconductor device require a large capacity, and others do a small leakage current rather than a large capacity. It is thus likely that when Ta2O5 is used in a capacitor insulation film, it will not meet the requirement that the leakage current should be small. The above-described problem will be solved if a capacitor using high dielectric materials and a capacitor having a small leakage current are manufactured separately from each other; however, manufacturing costs for the device will increase remarkably.
The use of a capacitor insulation film having a high dielectric constant has conventionally been considered in order to reduce the area of capacitors. Since, however, such a capacitor insulation film increases a leakage current, it is inapplicable to a capacitor that requires a small leakage current. Moreover, the separate manufacturing of a capacitor using high dielectric materials and a capacitor having a small leakage current causes an upswing in manufacturing costs.